Radio distributing system



*HAUWMMWMWMMWJ y March 16 1926'. 1,577,106

E: E. CLEMENT liAb'Io DISTRIu-TING SYSTEM original Fileg Sept. 25, 192.4

Patented Mr.' 16, 1926.

UNITED vSTATES PATENT oFricE.

EDWARD E. CLEMENT, F WASHDVGTCN', DISTRICT 0F COLUMBIA,.ASSIGNOB-'TOEDWARD F. COLLADAY, OF WASHINGTON, DISTRICT 0l' CDLUMBIA.

nemo nisrniaurii srsrnn.

Application led September 25, 1924, Serial No. 739,832. RenewedFebruary-11; 1926.

To all whom t may concern:

-Be it known'that I, EDWARD E. CLEMENT, acitizen of the United States,residin at Washington, iii the District of Colum ia, l have inventedcertain new and useful Improvenients in Radio Distributing Systems, ofwhich the following is a speci cation, reference being had therein tothe accompanying drawings.

My invention relates toradiophone exclian e systems andI has for itsobject to simp ify and improve methods of controlling the broadcastdistribution of 1ntelligenoe. 15 Brieliy stated, the inventioncompilises a radio-wire system, in which two sets of waves are radiatedat diiferent frequencies, preferably from the central statioii, and bothsets are received at each subscribers station, and bv means cf a specialmechanism, the combined or resultant potentials are impressed upon thesubscribers circuit, whereby oscillations at a frequency equivalent tothe beat or differential between the two primary frequencies, will, beproduced in the subscribers line to central,` which is tuned to saidbeat frequency. The oscilla.- tions thus set up in this resonatingcircuit are of long wave length, preferably of the $0 order of 10,000meters, which corresponds to a frequency of kilo cycles per second.` Ido not restrict myself to this particular frequency of wave length, butin'the av- A erage local subscribers telephone circuit,-

I have found suchl wave lengths to be suitable. At the central stationend of the line, n detctor, with or with'anipliliers, (both radio andaudio), receives the radio oscillations, detectsand rectities the same,and

l returns' corresponding audio frequency waves over the line to thesubscribers station, where they are rendered intelligible by suitablereceiving apparatus, not responsive to the primary or beat waves.

I shall describe .and illustrate the wave transformation herein as beingfrom primary to beat wave frequency, and 'then through a central oiiicedetector to audio frequency, so that audio frequency waves will flowback through the subscribers line.Av

With this specific form of the invention, the subscriber needs nospecial receiving apparatus, and may even use his ordinary' telephonereceiver for receiving the medidations bruglit in on the radio carrierwaves. It is obvious however, that instead of using this very simplearrangement,l I may4 cause the beat waves produced at the substation tooscillate in the line, so as to affect and be amplified by a radioamplifier tube or tubes, that is to say, in one or mre stages, 'at thecentral station, and sent back over the line thus amplified, to bepicked -up by the subscriber, anddetected, rectified.and renderedaudible at his station in the usual 66 way. 1 Certain advantages inherein this ar rangement at the central oiiice. One is in respect to thesimplicity of line connections, since all radio transmission isthrough'the 70 ether, and the only terminal attachmentsnecessary aremultipled taps across the lines, each containin the tuning elements,andone coil. of a coup er.A Aftbo'thendsA of the line, these are theonly'elements that need physi- 76 cal attachment thereto, and the tuningis such that audio frequency'telephone cur\ rents or batterycurrents-'are entirely unaffected thereby. Another advanta. e vat thecentral otlice is the concentration o detector tubes and circuits atcentral with the battery'l l supply and where constant inspection andcare are rendered easy and simple, 4 This system isintended to be usedfor" distant receiving and distribution or for- 85' local-broadcasting.For distant receivin the central oiiice apparatus includes'a tunedreceiving antenna circuit and a relay trans-1 mitter, which sends outthe saine radio waves amplified; also a local heterodyning trans 90nutter with a properly tuned aerial.' The modulations inthis case arecarried on the relayed waves, and the local heterodyne waves may beunmodulated. Where local. s -broadcastiiiv is desired however, Iafsecond5 modulated local oscillator circuit pi'o-v vided, which takes the placeof the rela transmitter for distantwaves. -Thirs wit two localoscillators, it follows that. eithertrain of waves or both may bemodulated 10 and this affords means to ive' out localgffv programslimited tothe su scribersonl without interfering with individual sul?)7scribers reception of distant stations-when practiced with independentapparatus. l0' My invention is lillustrated in the accom# panyingdrawings, in wliic Fig. 1 is adiagram showing a, coinpletef;i Y

equipment for practicing the invention, with vacuum tube detectors usedat both the subscribers and central stations.

Fig. 2 is a similar diagram of a fragment of the subscribers circuitshowing a crystal detector used in lace of the vacuum tube.

Referring to ig. 1, at the central station are indicated a radioreceiving and relaying apparatus RRand local oscillator LO.

The radio relaying apparatus RR has tuned antenna circuits 1 and 1, thelocal oscillator has a tuned antenna circuit 2. The radio relay may sendout its local reinforced waves on a separate aerial, or on the un- ]5tenne 1 or the antenna 2, as found expedient in practice. It is quiteobvious that interference between these trains of waves can produce noill e'ect, since they are intended to heterodyne at the subscribersstation and 0 in the aubscribers wired line circuit. At the subscribersstation 3 is one antenna circuit `tuned to the frequency'transmitted bythe radio relay RR, and 4 is a similar antenna circuit tuned to thefrequency of the cenu tral oiee local oscillator LO. AIf it be desiredto avoid tuning entirely at the subscribers station, it may be done inthe following manner: provide the radio relay set RR with either audioor rad'o means (such as a rimary heterodyne circuit) to change the reuency of the modulated waves received rom distant stations over theantenna 1, so that they will always go out locally on a constant wavelength. In such case, the local oscillator LO would also be tuned for aconstant wave length, and it necessarily follows that the tuning of thesubscribers antennae 3 and 4 may then be for constant wave lengths aswell as that of any local resonating circuit connected therewith. y

At the subscribers station I have shown the usual telephone set TS and ajack J bridged across the lim` to receive a plug P constituting theterminal of a local receiving circuit RC containing the telephonereceiver TC and talking condenser AC, the

urpose of this being to prevent closing the line for battery currentwhile listening to the relayed and amplified audio frequency currentscoming from central.

At the central station J-,J represent the ordinary standard switchboardterminals of any desired type, to which the line 5-6 is connected fortelephone communication with the suhscribers station SS. The' dottedlines in the middle of the figure represent that portion of the linewhich extends .between the subscribers station and the 'central olice.Across the ends I'brid e tuning elements I--Il and VC-VC, and cou lercoils C* and C. The line circuit is tun by means of these devices, andis maintained in oscillation durin receiving. a

At the subscr rs station the detector tube D has its rid circuit 8coupled through the coils'C an C to the antenna circuits; and its platecircuit 9 coupled to the line through the coils C2. The input circuit 8of the tube may be tuned by means of bridged condenser VGZ, to the meanfrequency of the waves received from the two antenna circuits 3 and 4,and the output circuit 9 including one side of the coupler C is tuned bymeans of the condenser VC* to the beat frequency, the other side of thecoupler C2 being similarly tuned by condenser VC. As usual inhetcrodyning vcircuits, the couiler C2 acts as a tuned filter to passonly the beat or long waves to line. The

central office coupler Ca has its secondary coil connected to the gridcircuit of a detector tubel', whoseplate circuit 7 is connected to theprimary of an audio frequency transformer AT, the secondary of which isbridged across the line wires 5 6. The long or beat waves sont over theline from the subscribers station ure thus demodulated and audiofrequent-v waves are fed back over the line to the subscribers station,where they become intelligible in the receiving instrument TC or itsequivalent. It is obvious that any desired number of stages ofsuper-audio frcquenc amplification, or audio frequency ampli lcation maybe inserted before and after the detector tube 7'. This use however ofan amplifier per line or a plurality of amplifiers per line in a systemfor distributing broadcast matter, is not claimed herein, beingdescribed' and claimed in m co nding application Serial No. 89,410, fied ebruary 19, 1926.

Fig. 2 shows a form of crystal detector circuit which may be used at thesubscribers sation instead of the vacuum tube detector circuit ofFig. 1. In vthis case the cou lers C- to tie 'mean of the receivedfrequenciesand to their beat frequency respectively. I

What I cla'im is:

1. In a radiophone exchange system, u. central station and subscribersstations and wired line circuits interconnecting them, means to transmitmodulated waves at radio frequency, means at the central station totransmit waves at heterodvning frequenciesv therefor, means at thesubscribers stations for receiving both frequencies, means caus-l ingthem by heterodynmg to reduce in the su scribcrs line circuit a beatrequenc and means in said circuit'at the centrale ation for detectingand rendering intelligible .to

the subscriber the modulations carried upon original carrier waves, andtransferred therefrom to the beat waves.

2. In a radiophone exchange system, a.

central station and subscribers* stations with wired line circuitsintcroonncctin them, means for transmitting modulat radio waves over thearea containing the subscriband Cz are tuned as before lll 1 also at thecentra ers stations, means at the central station for relayingandlamiliying said' wavesz means station for producmg and radiatingwaves at heterodyne frequencies,

means at a subscribers station for receiving ers stations, means at thecentral station for relaying and amplifying said waves, means also atthe central station for producing and radiating Waves at heterodyne'frequencies, means at the subscribers stations for receiving both theoriginal and heterodyning waves, means including a detector forimpressing the oscillating potentials of said waves upon the subscribersline circuits so as to roduce' modulated beat frequency waves t erein,detector means for said beat waves connected .with a ,subscribers lineat the central station, and means at the sub'- scribcrs stationresponsive to ,saidy :nodu- In testimony whereof I hereunto'aix mysignature. l

EDWARD E. CLEMENT.

